Bacteriorhodopsin is the prototype of seven-helical integral membrane proteins, such as G protein-coupled receptors. At 1.55 E resolution its transmembrane helix G is revealed to contain a pi-bulge which is stabilized by water molecules. After the pi-bulge, the alpha helical structure of helix G resumes on the cytoplasmic side of this bulge, but in a direction tilted away from the center by about 15 degrees. This type of non-proline kink of an alpha helix has previously only been reported for a small number of soluble proteins. We propose a functional role for the waters in the cytoplasmic half-channel and the altered hydrogen bonding pattern of helix G in the photocycle.